Time course of congener uptake and elimination in rats after short-term inhalation exposure to an airborne polychlorinated biphenyl (PCB) mixture

Transcriptome sequencing of 3,3',4,4',5-Pentachlorobiphenyl (PCB126)-treated human preadipocytes demonstrates progressive changes in pathways associated with inflammation and diabetes

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that accumulate in adipose tissue and have been associated with cardiometabolic disease. We have previously demonstrated that exposure of human preadipocytes to the dioxin-like PCB126 disrupts adipogenesis via the aryl hydrocarbon receptor (AhR). To further understand how PCB126 disrupts adipose tissue cells, we performed RNAseq analysis of PCB126-treated human preadipocytes over a 3-day time course. The most significant predicted upstream regulator affected by PCB126 exposure at the early time point of 9 h was the AhR. Progressive changes occurred in the number and magnitude of transcript levels of genes associated with inflammation, most closely fitting the pathways of cytokine-cytokine-receptor signaling and the AGE-RAGE diabetic complications pathway. Transcript levels of genes involved in the IL-17A, IL-1β, MAP kinase, and NF-κB signaling pathways were increasingly dysregulated by PCB126 over time. Our results illustrate the progressive time-dependent nature of transcriptional changes caused by toxicants such as PCB126, point to important pathways affected by PCB126 exposure, and provide a rich dataset for further studies to address how PCB126 and other AhR agonists disrupt preadipocyte function. These findings have implications for understanding how dioxin-like PCBs and other dioxin-like compounds are involved in the development of obesity and diabetes.

BMI modifies the association between dietary intake and serum levels of PCBs

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants that are carcinogenic, neurotoxic, and endocrine disrupting in humans. Although diet is the primary source of exposure, there is no consensus on the association between dietary intake and serum PCBs. Additionally, body mass index (BMI) - with its inverse association with serum PCBs - may play a role in the association, which has never been studied. Therefore, we aimed to examine the association between dietary intake and serum levels of PCBs, and whether the association was modified by BMI. We used data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004, including 1531 participants. We estimated dietary intake of PCBs using the 24-hour diet recall, USDA Food Composition Intake Database, and PCB content in foods from the Canada Total Diet Study. Serum PCBs were measured by high-resolution gas chromatography-mass spectrometry (HRGC-HRMS). We used linear regression to examine the associations of dietary PCB intake with serum levels of seven PCB congeners and six PCB metrics. Further, we explored the role of BMI in the associations. We found that participants who were older and non-Hispanic tended to have a higher serum level of ∑37-PCB. In addition, we observed positive associations between dietary intake and serum PCBs for: PCB 105, 118, 126, 138 + 158, and 153 (P value ranges 0.005-0.03); seven PCB indicators (P value = 0.03) and the sum of 37 PCBs (P value = 0.04). Furthermore, we observed an effect modification by BMI (P for interaction = 0.01 for ∑37-PCBs), with stronger associations in underweight or normal-weight individuals, and no association in overweight and obese individuals. In conclusion, within a cross-sectional, nationally representative sample of the US population, dietary PCB intake was positively associated with serum PCBs and the association was modified by BMI. Additional studies are warranted to replicate and confirm this effect modification.

Comprehensive Subchronic Inhalation Toxicity Assessment of an Indoor School Air Mixture of PCBs

Few in vivo inhalation studies have explored the toxicity of environmentally relevant mixtures of polychlorinated biphenyls (PCBs). The manufacture of industrial PCBs was banned in 1978, but PCBs continue to be formed in industrial and consumer products. Schools represent a significant source of airborne exposures to legacy and nonlegacy PCBs, placing children at risk. To evaluate the impact of these exposures, we generated an airborne mixture of PCBs, called the School Air Mixture (SAM), to match the profile of an older school from our adolescent cohort study. Female Sprague-Dawley rats were exposed either to SAM or filtered air in nose-only exposure systems, 4 h/day for 4 weeks. Congener-specific air and tissue PCB profiles were assessed using gas chromatography with tandem mass spectrometry (GC-MS/MS). PCB exposures recapitulated the target school air profile with a similarity coefficient, cos θ of 0.83. PCB inhalation yielded μg/g ∑209 PCB levels in tissues. Neurobehavioral testing demonstrated a modest effect on spatial learning and memory in SAM-exposed rats. PCB exposure induced oxidative stress in the liver and lungs, affected the maturational stages of hematopoietic stem cells, reduced telomerase activity in bone marrow cells, and altered the gut microbiota. This is the first study to emulate PCB exposures in a school and comprehensively evaluate toxicity.

Fatty liver and impaired hepatic metabolism alter the congener-specific distribution of polychlorinated biphenyls (PCBs) in mice with a liver-specific deletion of cytochrome P450 reductase

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver-specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wild-type (WT) mice. Eight-week-old male WT (M_WT, n = 3), male KO (M_KO, n = 5), female WT (F_WT, n = 4), and female KO mice (F_KO, n = 4) were exposed orally to Aroclor 1254. PCBs were quantified in adipose, blood, brain, and liver tissues by gas chromatography-mass spectrometry. The ΣPCB levels followed the rank order adipose > liver ∼ brain > blood in WT and adipose ∼ liver > brain > blood in KO mice. PCB levels were much higher in the liver of KO than WT mice, irrespective of the sex. A comparison across exposure groups revealed minor genotype and sex-dependent differences in the PCB congener profiles (cos Θ > 0.92). Within each exposure group, tissue profiles showed small differences between tissues (cos Θ = 0.85 to 0.98). These differences were due to a decrease in metabolically more labile PCB congeners and an increase in congeners resistant to metabolism. The tissue-to-blood ratio of PCBs decreased for adipose, increased for the brain, and remained constant for the liver with an increase in chlorination. While these ratios did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was reasonable. Although the distribution of PCBs differs between KO and WT mice, the magnitude of the partitioning of PCBs from the blood into tissues can be approximated using composition-based models.

Fatty liver and impaired hepatic metabolism alter the congener-specific distribution of polychlorinated biphenyls (PCBs) in mice with a liver-specific deletion of cytochrome P450 reductase

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver-specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wild-type (WT) mice. Eight-week-old male WT (M_WT, n = 3), male KO (M_KO, n = 5), female WT (F_WT, n = 4), and female KO mice (F_KO, n = 4) were exposed orally to Aroclor 1254. PCBs were quantified in adipose, blood, brain, and liver tissues by gas chromatography-mass spectrometry. The ΣPCB levels followed the rank order adipose > liver ∼ brain > blood in WT and adipose ∼ liver > brain > blood in KO mice. PCB levels were much higher in the liver of KO than WT mice, irrespective of the sex. A comparison across exposure groups revealed minor genotype and sex-dependent differences in the PCB congener profiles (cos Θ > 0.92). Within each exposure group, tissue profiles showed small differences between tissues (cos Θ = 0.85 to 0.98). These differences were due to a decrease in metabolically more labile PCB congeners and an increase in congeners resistant to metabolism. The tissue-to-blood ratio of PCBs decreased for adipose, increased for the brain, and remained constant for the liver with an increase in chlorination. While these ratios did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was reasonable. Although the distribution of PCBs differs between KO and WT mice, the magnitude of the partitioning of PCBs from the blood into tissues can be approximated using composition-based models.

Excretion characteristics and tissue accumulation of tetrabromobisphenol-A in male rats after sub-chronic inhalation exposure

Tetrabromobisphenol-A (TBBPA) is an emerging organic pollutant and a commonly used brominated flame retardant that has received much attention owing to its toxicity. Although TBBPA is ubiquitously detected in atmospheric particulate matter and dust, few studies have investigated the sub-chronic inhalation exposure to TBBPA. To further understand the excretion characteristics and tissue accumulation of TBBPA after inhalation exposure, we used the rat model to conduct a sub-chronic inhalation exposure study. Male rats were administered with different doses of aerosol TBBPA (12.9, 54.6, 121.6, and 455.0 mg/m³). TBBPA was found in the excretion (feces and urine) and all the target tissues (lung, liver, heart, thymus gland, spleen, testicles, muscles, kidneys, brain and serum). Feces were the main route of excretion, which contributed 19.18% to 72.54% (urine <0.10%). TBBPA excretion through feces following inhalation administration was much higher than that following oral and dermal exposure, thereby indicating lower bioavailability of TBBPA under inhalation exposure. Liver and serum showed higher levels of TBBPA compared with those of other tissues, thereby suggesting tissue-specific accumulation of TBBPA in rats. Owing to the relative non-invasiveness of serum sampling and greatest TBBPA concentration among the tissues, serum is a suitable matrix for estimation of TBBPA bioaccumulation after inhalation exposure.

Human health risks due to airborne polychlorinated biphenyls are highest in New Bedford Harbor communities living closest to the harbor

In response to concerns raised by communities surrounding the New Bedford Harbor Superfund site, we completed a field and modeling study that concluded the harbor is the primary source of polychlorinated biphenyls (PCBs) in air around the harbor. The follow-up question from residents was whether the PCBs measured in air pose a risk to their health. The US Environmental Protection Agency focuses their site-specific, risk-based decisions for site clean-up on cancers. We focused our assessment on the non-cancer effects on the thyroid based on the congener specific patterns and concentrations of PCBs measured in air near and distant to the harbor. Human and animal studies of PCB-induced effects on the thyroid provide evidence to support our analysis. Drawing from the published toxicological data, we used a Margin of Exposure (MOE) approach to derive a human-equivalent concentration in air associated with human health effects on the thyroid. Based on the MOEs calculated herein, evaluation of the MOE indicates that changes in thyroid hormone levels are possible among people living adjacent to the Harbor. Changes in thyroid hormone levels are more likely among people who live near the harbor compared to residents living in areas distant from the harbor. This risk assessment documents potential health risks associated with proximity to a marine Superfund Site using site-specific ambient air PCB congener data.

3-(3,5-Dichlorophenyl)benzene-1,2-diol

The title structure [systematic name: 4-(3,5-dichlorophenyl)benzene-1,2-diol], C12H8Cl2O2, is a putative metabolite of 3,5-dichlorobiphenyl (PCB 14). The dihedral angle between the two benzene rings of the title compounds is 58.86 (4)°. In the crystal, it displays intra and intermolecular O-H···O hydrogen bonding and intermolecular O-H···Cl hydrogen···chlorine interactions.

Persistent organic pollutants as predictors of increased FSH:LH ratio in naturally cycling, reproductive age women

Although several recent studies suggest endocrine disrupting compounds, such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p', DDE), and hexachlorobenzene (HCB), target different organs and systems in the body, their impact on female reproductive function in humans is not well characterized. We seek to determine the relationship between several known endocrine disrupting compounds and a marker of ovarian responsivity, the FSH:LH ratio (higher ratio indicates less ovarian responsivity). For this analysis, 169 naturally cycling women between 21 and 38 years of age completed interviews and had their blood drawn on day 3 of their menstrual cycle for analyses of toxicants, gonadal sex hormones (E₂ and P₄), and gonadotropins (FSH and LH). PCB congeners were classified into five groups based on their environmental persistence, distribution in human tissue, and toxicological action, reflecting the structure, mechanism, and known biological activity of individual PCB congeners. For every unit (ppb) increase in the level of the estrogenic PCB group, there was a 5-fold greater risk of a FSH:LH ratio ≥ 2, controlling for individual differences in age, percent body fat, cycle day 3 estradiol levels, parity, alcohol use and cigarette smoking in the past year (exp[ß] = 5; p = ≤0.01). PCB congeners identified as estrogenic were analyzed individually, and, of the 19 potentially estrogenic congeners, five were significantly, and positively related to an increased FSH:LH ratio. Four of these congeners are non-persistent, easily volatilize in the environment, and are easily metabolized, and hence, are indicative of very recent or current exposure. p,p'-DDE and HCB were not associated with FSH:LH ratio. We find a clinical indicator of ovarian responsivity, FSH:LH ratio, is associated with a specific group of estrogenic PCBs. These congeners may become airborne when they volatilize from dredged PCB-contaminated soil or from indoor PCB-containing window caulk and sealants in older buildings leading to inhalation exposure. PCB exposure, particularly to non-persistent, estrogenic congeners, may pose an unrecognized threat to female fecundity within the general population.

Generation of Localized Surface Plasmon Resonance Using Hybrid Au-Ag Nanoparticle Arrays as a Sensor of Polychlorinated Biphenyls Detection

In this study, the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic nanoparticle arrays (PNAs) were designed to investigate their extinction spectra of the localized surface plasmon resonances (LSPRs). First, their simulating extinction spectra were calculated by discrete dipole approximation (DDA) numerical method by changing the media refractive index. Simulation results showed that as the media refractive index was changed from 1.0 to 1.2, the maximum peak intensity of LSPRs spectra had no apparent change and the wavelength to reveal the maximum peak intensity of LSPRs spectra was shifted lower value. Polystyrene (PS) nanospheres with two differently arranged structures were used as the templates to deposit the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic PNAs by evaporation method. The hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate PNAs were grown on single crystal silicon (c-Si) substrates, and their measured extinction spectra were compared with the calculated results. Finally, the fabricated hexagonal lattices of triangular PNAs were investigated as a sensor of polychlorinated biphenyl solution (PCB-77) by observing the wavelength to reveal the maximum extinction efficiency (λ_max). We show that the adhesion of β-cyclodextrins (SH-β-CD) on the hybrid Au–Ag hexagonal lattice of triangular PNAs could be used to increase the variation of λ_max. We also demonstrate that the adhesion of SH-β-CD increases the sensitivity and detection effect of PCB-77 in hexagonal lattice of triangular PNAs.

PAMAM dendrimers as nano carriers to investigate inflammatory responses induced by pulmonary exposure of PCB metabolites in Sprague-Dawley rats

Polychlorinated biphenyls (PCBs) persist and accumulate in the ecosystem depending upon the degree of chlorination of the biphenyl rings. Airborne PCBs are especially susceptible to oxidative metabolism, yielding mono- and di-hydroxy metabolites. We have previously demonstrated that 4-chlorobiphenyl hydroquinones (4-CB-HQs) acted as cosubstrates for arachidonic acid metabolism by prostaglandin H synthase (PGHS) and resulted in an increase of prostaglandin production in vitro. In the present study, we tested the capability of 4-CB-HQ to act as a co-substrate for PGHS catalysis in vivo. BQ and 4-CB-2',5'-HQ were administered intratracheally to male Sprague-Dawley rats (2.5 μmol/kg body weight) using nanosized polyamidoamine (PAMAM) dendrimers as carriers. We found that 24 h post application, PGE2 metabolites in kidney of rats treated with 4-CB-2',5'-HQ were significantly increased compared to the controls. The increase of PGE2 metabolites was correlated with increased alveolar macrophages in lung lavage fluid. The elevation of PGE2 synthesis is of great interest since it plays a crucial role in balancing homeostasis and inflammation where a chronic disturbance may increase risk of cancer. PAMAM dentrimers proved to be an effective transport medium and did not stimulate an inflammatory response themselves.

Chiral polychlorinated biphenyls: absorption, metabolism and excretion--a review

Seventy eight out of the 209 possible polychlorinated biphenyl (PCB) congeners are chiral, 19 of which exist under ambient conditions as stable rotational isomers that are non-superimposable mirror images of each other. These congeners (C-PCBs) represent up to 6 % by weight of technical PCB mixtures and undergo considerable atropisomeric enrichment in wildlife, laboratory animals, and humans. The objective of this review is to summarize our current knowledge of the processes involved in the absorption, metabolism, and excretion of C-PCBs and their metabolites in laboratory animals and humans. C-PCBs are absorbed and excreted by passive diffusion, a process that, like other physicochemical processes, is inherently not atropselective. In mammals, metabolism by cytochrome P450 (P450) enzymes represents a major route of elimination for many C-PCBs. In vitro studies demonstrate that C-PCBs with a 2,3,6-trichlorosubstitution pattern in one phenyl ring are readily oxidized to hydroxylated PCB metabolites (HO-PCBs) by P450 enzymes, such as rat CYP2B1, human CYP2B6, and dog CYP2B11. The oxidation of C-PCBs is atropselective, thus resulting in a species- and congener-dependent atropisomeric enrichment of C-PCBs and their metabolites. This atropisomeric enrichment of C-PCBs and their metabolites likely plays a poorly understood role in the atropselective toxicity of C-PCBs and, therefore, warrants further investigation.

Polychlorinated biphenyls and organochlorine pesticides in atmospheric particulate matter of Northern China: distribution, sources, and risk assessment

The objectives of this work are to track the contamination levels, distribution characteristics, and sources of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in atmospheric particulate matter (APM) of Northern China and to provide more comprehensive and fundamental data for risk assessment of organochlorine contaminants (OCs) in environments. Samples were extracted and purified by the microwave-assisted extraction and solid-phase extraction system, respectively. PCBs and OCPs were analyzed by gas chromatograph-mass spectrometer. The concentrations of ΣPCBs and ΣOCPs ranged from 0.73 to 112.65 ng/g and 0.14 to 34.73 ng/g, respectively. PCBs in atmospheric particulates collected from Shijiazhuang City had the highest concentration, whereas OCP congeners were at the relatively low levels. However, the highest concentration of OCPs occurred in Yongning City. The principal component analysis indicated that the predominant compositions of PCBs in most of samples were tetrachlorobiphenyl (Tetra-CB), pentachlorobiphenyl (Penta-CB), hexachlorobiphenyl (Hexa-CB), and heptachlorbiphenyl (Hepta-CB), while hexachlorocyclohexanes (HCHs), DDTs, chlordanes, and endosulfans were the dominant components of OCPs, which was attributed to their application characteristics. OCs in those particles were further used to assess a potential cancer risk to humans via ingestion, dermal contact, and inhalation. Cancer risk was evaluated in airborne particles caused by PCBs and OCPs. TEQPCBs values suggested that the representative areas were subject to different pollution degrees. However, the pollution of OCPs in certain areas should be a concern due to 41.6% of the high risk, which could pose a potential risk to organisms.

Toxicity Evaluation of Exposure to an Atmospheric Mixture of Polychlorinated Biphenyls by Nose-Only and Whole-Body Inhalation Regimens

The health risk of inhalation exposure to polychlorinated biphenyls (PCB) cannot be assessed with high confidence due to the lack of rigorous inhalation studies. One uncertainty rests on exposure regimen, as whole-body exposure systems allow oral PCB intake that confounds the exposure. We conducted contemporaneous PCB inhalation exposures with whole-body and nose-only exposure methods. Female Sprague-Dawley rats were concurrently exposed to vapor-phase PCBs (533 ± 93 μg/m(3)) generated from PCB11-supplemented Chicago Air Mixture resembling the Chicago airshed, 4 h/day, 6 days/week, for 4 weeks. Congener-specific analysis showed 1.5-fold higher ∑PCBs in the lungs of nose-only exposed than the whole-body exposed animals (p = 0.0024). Higher ∑PCB concentrations were also found in the sera, livers, brains, and adipose tissue of nose-only exposed animals (1.1-1.5-fold), but these increases were not statistically significant. Congener profiles of five tissue types were dominated by PCB 28/31 and higher-chlorinated congeners in both groups reflecting rapid metabolism of other lower-chlorinated PCBs. No toxicity was seen regarding metabolic enzyme expression, glutathione, or histopathology. However, diminished weight gain and reduced plasma total thyroxine levels were found in both groups compared with controls, after exposure to 76 μg/m(3) ∑PCBs as adjusted for continuous exposure. Hepatic lipid peroxidation was also elevated in the nose-only group. Our study shows that prolonged nose-only exposure was well-tolerated and eliminated the need for housing animals outside the vivarium, thus was preferred for long-term PCB inhalation studies.

Inhalation of Polychlorinated Biphenyls (PCB) Produces Hyperactivity in Rats

Attention deficit hyperactivity disorder (ADHD) is a serious behavioral syndrome seen in children, and more common in males than females. There is increasing evidence that prenatal and/or early life exposure to persistent organic pollutants (POP) such as polychlorinated biphenyls (PCB) is associated with increased risk of ADHD occurrence. While PCB exposure is usually attributed to ingestion of contaminated food, recent reports of elevated PCB concentrations in indoor air, especially in schools, raised concern regarding inhalation as an important route of exposure to PCB with consequent effects on neurobehavior. The effects of exposure to air contaminated with Aroclor 1248 or contaminated sediment (SED) from the St. Lawrence River were examined on operant behavior of male and female Sprague-Dawley rats. Data showed that relative to controls, vapor-phase inhalation of PCB, whether from blowing air over Aroclor 1248 or from blowing air over sediment contaminated with PCB, resulted in hyperactivity and impatience in rats, more pronounced in males than females. These results are consistent with the hypothesis that inhalation of PCB may contribute to behavioral abnormalities in children.

Metabolism and metabolites of polychlorinated biphenyls

Abstract The metabolism of polychlorinated biphenyls (PCBs) is complex and has an impact on toxicity, and thereby on the assessment of PCB risks. A large number of reactive and stable metabolites are formed in the processes of biotransformation in biota in general, and in humans in particular. The aim of this document is to provide an overview of PCB metabolism, and to identify the metabolites of concern and their occurrence. Emphasis is given to mammalian metabolism of PCBs and their hydroxyl, methylsulfonyl, and sulfated metabolites, especially those that persist in human blood. Potential intracellular targets and health risks are also discussed.

Exposure to and health effects of volatile PCBs

INTRODUCTION

Polychlorinated biphenyls (PCBs) are persistent, lipophilic contaminants that are known to increase risk of a number of human diseases. Although ingestion of animal fats is a major route of exposure, there is increasing evidence that inhalation of vapor-phase PCBs is also important and may be as or even more important than ingestion under some circumstances.

METHODS

The evidence that inhalation of PCBs may cause cancer, heart disease, hypertension, and diabetes is reviewed and presented in this report.

RESULTS

PCBs are known human carcinogens. A husband and wife, occupationally required to 'smell' PCB-containing oils, both developed thyroid cancer, malignant melanoma/severely melanocytic dysplastic nevus (a precursor to malignant melanoma) and the husband, a non-smoker, developed and died of lung cancer. The serum of both had highly elevated concentrations of lower chlorinated, volatile PCB congeners. In other studies, residents living near PCB-containing hazardous waste sites, and thus breathing PCB-contaminated air, have elevated rates of hospitalization for cardiovascular disease, hypertension, diabetes and reduced cognitive performance, whereas other studies in defined populations show that there is an elevated risk of all of these diseases in individuals with elevated serum PCBs.

CONCLUSIONS

These results are consistent with the conclusion that inhaled PCBs can increase risk of cancer, cardiovascular disease, hypertension, diabetes and reduce cognitive function.

Changes of polybrominated diphenyl ether concentrations in ducks with background exposure level and time

To reveal what degree bioaccumulation of polybrominated diphenyl ethers (PBDEs) depends on exposure time and other factors, we conducted a semi-field experiment for a year (June 2008-June 2009) in a village in an e-waste recycling site in Taizhou, China. Approximately one hundred of juvenile ducks (Anas domestica Linnaeus) were entrusted to a villager. The ducks lived and forged in a PBDE-polluted pond from the late March to the end of November. Fish and mudsnails that were heavily polluted by PBDEs were main food. In cold days (from December to the middle March), the ducks lived in the villager' house, and mainly fed on paddy, which contained lower concentrations of PBDEs than fish and mudsnails. The female ducks were sampled for PBDE analysis every three months. We found that the ∑PBDE concentrations in duck liver, muscle, lung and brain fluctuated greatly with the changes of exposure levels that were determined by the environment and diets, but the ∑PBDE concentrations in fat tissue increased successively with time. Congener analysis demonstrated that the successive increase in the ∑PBDE concentrations with time in fat tissue was due to the successive increase in BDE-209, -183 and -153 concentrations, with large fluctuations of low brominated congeners. The results show that PBDE concentrations in liver, muscle, lung and brain tissues heavily depends on exposure levels rather than exposure time. In fat tissue, by contrast, PBDE concentrations (mainly high brominated congeners) slightly depends on exposure levels but heavily depend on time relative to other tissues, implying that high brominated congeners seem to have longer half-lives than low brominated congeners in fat tissue.

Disposition of phenolic and sulfated metabolites after inhalation exposure to 4-chlorobiphenyl (PCB3) in female rats

PCBs, such as PCB3, are air contaminants in buildings and outdoors. Metabolites of PCB3 are potential endocrine disrupting chemicals and genotoxic agents. We studied the disposition of phenolic and sulfated metabolites after acute nose-only inhalation exposure to airborne PCB3 for 2 h in female rats. Inhalation exposure was carried out in three groups. In the first group, rats exposed to an estimated dose of 26 μg/rat were euthanized at 0, 1, 2, and 4 h after exposure. Highest concentrations of phenols and sulfates were observed at 0 h, and the values were 7 ± 1 and 560 ± 60 ng/mL in serum, 213 ± 120 and 842 ± 80 ng/g in liver, 31 ± 27 and 22 ± 7 ng/g in lung, and 27 ± 6 and 3 ± 0 ng/g in brain, respectively. First-order serum clearance half-lives of 0.5 h for phenols and 1 h for sulfates were estimated. In the second group, rats exposed to an estimated dose of 35 μg/rat were transferred to metabolism cages immediately after exposure for the collection of urine and feces over 24 h. Approximately 45 ± 5% of the dose was recovered from urine and consisted mostly of sulfates; the 18 ± 5% of the dose recovered from feces was exclusively phenols. Unchanged PCB3 was detected in both urine and feces but accounted for only 5 ± 3% of the dose. Peak excretion of metabolites in both urine and feces occurred within 18 h postexposure. In the third group, three bile-cannulated rats exposed to an estimated dose of 277 μg/rat were used for bile collection. Bile was collected for 4 h immediately after 2 h exposure. Biliary metabolites consisted mostly of sulfates, some glucuronides, and lower amounts of the free phenols. Control rats in each group were exposed to clean air. Clinical serum chemistry values, serum T4 level, and urinary 8-hydroxy-2'-deoxyguanosine were similar in treated and control rats. These data show that PCB3 is rapidly metabolized to phenols and conjugated to sulfates after inhalation and that both of these metabolites are distributed to liver, lungs, and brain. The sulfates elaborated into bile are either reabsorbed or hydrolyzed in the intestine and excreted in the feces as phenols.

The fate of inhaled (14)C-labeled PCB11 and its metabolites in vivo

BACKGROUND

The production ban of polychlorinated biphenyl (PCB) technical mixtures has left the erroneous impression that PCBs exist only as legacy pollutants. Some lower-chlorinated PCBs are still being produced and contaminate both indoor and ambient air.

OBJECTIVES

To inform PCB risk assessment, we characterized lung uptake, distribution, metabolism and excretion of PCB11 as a signature compound for these airborne non-legacy PCBs.

METHODS

After delivering [(14)C]PCB11 to the lungs of male rats, radioactivity in 34 major tissues and 5 digestive matter compartments was measured at 12, 25, 50, 100, 200 and 720min postexposure, during which time the excreta and exhaled air were also collected. [(14)C]PCB11 and metabolites in lung, liver, blood, digestive matter, urine, feces, and adipose tissues were extracted separately to establish the metabolic profile of the disposition.

RESULTS

[(14)C]PCB11 was distributed rapidly to all tissues after 99.8% pulmonary uptake and quickly underwent extensive metabolism. The major tissue deposition of [(14)C]PCB11 and metabolites translocated from liver, blood and muscle to skin and adipose tissue 200min postexposure, while over 50% of administered dose was discharged via urine and feces within 12h. Elimination of the [(14)C]PCB11 and metabolites consisted of an initial fast phase (t½=9-33min) and a slower clearance phase to low concentrations. Phase II metabolites dominated in liver blood and excreta after 25min postexposure.

CONCLUSIONS

This study shows that PCB11 is completely absorbed after inhalation exposure and is rapidly eliminated from most tissues. Phase II metabolites dominated with a slower elimination rate than the PCB11 or phase I metabolites and thus can best serve as urine biomarkers of exposure.

Atmospheric polychlorinated biphenyls in Indian cities: levels, emission sources and toxicity equivalents

Atmospheric concentration of Polychlorinated biphenyls (PCBs) were measured on diurnal basis by active air sampling during Dec 2006 to Feb 2007 in seven major cities from the northern (New Delhi and Agra), eastern (Kolkata), western (Mumbai and Goa) and southern (Chennai and Bangalore) parts of India. Average concentration of Σ25PCBs in the Indian atmosphere was 4460 (± 2200) pg/m(-3) with a dominance of congeners with 4-7 chlorine atoms. Model results (HYSPLIT, FLEXPART) indicate that the source areas are likely confined to local or regional proximity. Results from the FLEXPART model show that existing emission inventories cannot explain the high concentrations observed for PCB-28. Electronic waste, ship breaking activities and dumped solid waste are attributed as the possible sources of PCBs in India. Σ25PCB concentrations for each city showed significant linear correlation with Toxicity equivalence (TEQ) and Neurotoxic equivalence (NEQ) values.

Sulfate conjugates are urinary markers of inhalation exposure to 4-chlorobiphenyl (PCB3)

PCBs are contaminants in the air of older buildings and cities, which raises the concern of inhalation exposure. No reliable biomarker of such exposure is available. We exposed rats to air containing 2 mg/m(3) PCB3 via nose-only inhalation for 2 h, collected urine, and analyzed it by LC/MS. Each rat inhaled an estimated dose of 35 μg PCB3, and excreted 27 ± 2% of it as sulfates within 24 h. Peak excretion occurred within 6 h. PCB sulfates were stable in urine for at least three days at room temperature without chemical preservatives. These data support the use of PCB sulfate conjugates as suitable urinary biomarkers of PCB3 and other airborne PCBs.

Elimination of inhaled 3,3'-dichlorobiphenyl and the formation of the 4-hydroxylated metabolite

The recent discovery of 3,3'-dichlorobiphenyl (CB11) as a byproduct of pigment manufacturing underscores the urgency to investigate its biological fate. The high level and ubiquity of atmospheric CB11 indicates that inhalation is the major route of exposure. However, few data on its uptake and elimination exist. A time course study was performed exposing male Sprague-Dawley rats to CB11 via nose-only inhalation with necropsy at 0, 4, and 8 h post exposure. An analytical method for CB11 and monohydroxylated metabolites employing pressurized liquid extraction and gas chromatography-mass spectrometry yielded efficient recovery of CB11 (73 ± 9%) and its metabolite 3,3'-dichlorobiphenyl-4-ol (4-OH-CB11) (82 ± 12%). Each rat was exposed to 106 μg/m(3) vapor-phase CB11 for 2 h and received an estimated dose of 1.8 μg. Rapid apparent first-order elimination of CB11 was found in lung, serum, and liver with half-lives of 1.9, 1.8, and 2.1 h, respectively. 4-OH-CB11 was detected in the liver but not the lung or serum of exposed animals and displayed apparent first-order elimination with a 2.4 h half-life. This study demonstrates rapid metabolism of CB11 and elimination of 4-OH-CB11 and suggests that the metabolite is not retained in the body but is susceptible to further biotransformation.

2,2',3,5',6-Pentachlorobiphenyl (PCB 95) and its hydroxylated metabolites are enantiomerically enriched in female mice

Epidemiological and laboratory studies link polychlorinated biphenyls and their metabolites to adverse neurodevelopmental outcomes. Several neurotoxic PCB congeners are chiral and undergo enantiomeric enrichment in mammalian species, which may modulate PCB developmental neurotoxicity. This study measures levels and enantiomeric enrichment of PCB 95 and its hydroxylated metabolites (OH-PCBs) in adult female C57Bl/6 mice following subchronic exposure to racemic PCB 95. Tissue levels of PCB 95 and OH-PCBs increased with increasing dose. Dose-dependent enantiomeric enrichment of PCB 95 was observed in brain and other tissues. OH-PCBs also displayed enantiomeric enrichment in blood and liver, but were not detected in adipose and brain. In light of data suggesting enantioselective effects of chiral PCBs on molecular targets linked to PCB developmental neurotoxicity, our observations highlight the importance of accounting for PCB and OH-PCB enantiomeric enrichment in the assessment of PCB developmental neurotoxicity.

Subchronic inhalation exposure study of an airborne polychlorinated biphenyl mixture resembling the Chicago ambient air congener profile

Although inhalation of atmospheric polychlorinated biphenyls (PCBs) is the most universal exposure route and has become a substantial concern in urban areas, research is lacking to determine the body burden of inhaled PCBs and consequent health effects. To reflect the Chicago airshed environment and mimic the PCB profile in Chicago air, we generated vapors from a Chicago air mixture (CAM). Sprague-Dawley rats were exposed to the CAM vapor for 1.6 h/day via nose-only inhalation for 4 weeks, 520 ± 10 μg/m(3). Congener-specific quantification in tissue and air samples was performed by gas chromatography-tandem mass spectrometry (GC/MS/MS). In contrast to the lower-chlorinated congener-enriched vapor, body tissues mainly contained tri- to hexachlorobiphenyls. Congener profiles varied between vapor and tissues and among different organs. The toxic equivalence (TEQ) and neurotoxic equivalence (NEQ) were also investigated for tissue distribution. We evaluated a variety of end points to catalogue the effects of long-term inhalation exposure, including immune responses, enzyme induction, cellular toxicity, and histopathologic abnormalities. Glutathione oxidized/reduced ratio (GSSG/GSH) was increased in the blood of exposed animals, accompanied by elevation of hematocrit. This study demonstrated that inhalation contributed to the body burden of mostly tri- to hexachlorobiphenyls and produced a distinct profile of congeners in tissue, yet minimal toxicity was found at this exposure dose, estimated at 134 μg/rat.

Serum PCB levels and congener profiles among teachers in PCB-containing schools: a pilot study

BACKGROUND

PCB contamination in the built environment may result from the release of PCBs from building materials. The significance of this contamination as a pathway of human exposure is not well-characterized, however. This research compared the serum PCB concentrations, and congener profiles between 18 teachers in PCB-containing schools and referent populations.

METHODS

Blood samples from 18 teachers in PCB-containing schools were analyzed for 57 PCB congeners. Serum PCB concentrations and congener patterns were compared between the teachers, to the 2003-4 NHANES (National Health and Nutrition Examination Survey) data, and to data from 358 Greater Boston area men.

RESULTS

Teachers at one school had higher levels of lighter (PCB 6-74) congeners compared to teachers from other schools. PCB congener 47 contributed substantially to these elevated levels. Older teachers (ages 50-64) from all schools had higher total (sum of 33 congeners) serum PCB concentrations than age-comparable NHANES reference values. Comparing the teachers to the referent population of men from the Greater Boston area (all under age 51), no difference in total serum PCB levels was observed between the referents and teachers up to 50 years age. However, the teachers had significantly elevated serum concentrations of lighter congeners (PCB 6-74). This difference was confirmed by comparing the congener-specific ratios between groups, and principal component analysis showed that the relative contribution of lighter congeners differed between the teachers and the referents.

CONCLUSIONS

These findings suggest that the teachers in the PCB-containing buildings had higher serum levels of lighter PCB congeners (PCB 6-74) than the referent populations. Examination of the patterns, as well as concentrations of individual PCB congeners in serum is essential to investigating the contributions from potential environmental sources of PCB exposure.